Temperature sensors having a temperature-sensitive element with platinum are known which are produced in thin-film technology in which platinum on a support substratum is diffused in layers of a few atoms. In maintaining a corresponding geometric structure such as meander form, there may be obtained with thin enough layers of a few atom layers a high enough ground resistance which, for such a temperature sensor, must lie in the range of 100 ohms. These thin-film sensors can only be used at lower temperatures in the range up to 400.degree. C., and below 600.degree. C. in any case since platinum vaporizes at higher temperatures. By this alone, there is a considerable change of resistance so that no reproducible results are longer possible because of the layer thickness of only a few atom layers.
Platinum wires have also been used as temperature sensors. To reach the large enough ground resistance, the wire would have to have a considerable length which even with winding in coil form would lead to a sensor with considerable outer dimensions which cannot be used in many areas where there is miniaturizing. Thick-layer pastes containing platinum are also known which have organic binders and solvents as other components. These are used as thick-film heating elements and reach their sufficient resistance based on the length of the heating element, and are used for pressure-setting temperatures usual in heating. Aside from the low specific resistance which would also lead only to very large sensor elements, these could not be used at temperatures higher than 600.degree. C. since there would no longer be reproducibility. In both cases, it is true that platinum is in a red glow from about 800.degree. C., but can no longer be used as a temperature sensor.
The applicant has found that no miniaturized temperature sensors are known for high temperature uses. Thermo elements which work with thermovoltages are used. A disadvantage here is that a definite surrounding temperature must be used as a reference temperature or a microprocessor be used. Such temperature coolers are expensive.